Traffic management for high-bandwidth switching

Abstract

In the subject system for a network switch may determine to transition the output port of the network switch between a store-and-forward (SAF) state and a cut-through (CT) state based on at least one factor. The network switch may determine, based on a condition of the output port, whether to transition the output port to a transition-cut-through (TCT) state or directly to a CT state when transitioning the output port to the CT state. When the output port is transitioned to the TCT state, the network switch may determine, based on the condition of the output port, whether to transition the output port to the CT state or to transition the output port back to the SAF state.

What is claimed is: 
     
       1. A network switch, comprising:
 at least one egress controller of an egress buffer component associated with an output port, the at least one egress controller configured to:
 determine to transition the output port of the network switch between a store-and-forward (SAF) state and a cut-through (CT) state based on at least one factor; 
 
 transition, based on a condition of the output port, the output port to a transition-cut-through (TCT) state or directly to a CT state when transitioning the output port to the CT state; and
 when the output port is transitioned to the TCT state, transition, based on the condition of the output port, the output port to the CT state or back to the SAF state. 
 
 
     
     
       2. The network switch of  claim 1 , wherein the at least one egress controller is further configured to:
 receive a CT request from an ingress tile, the CT request requesting a transition of the output port to the CT state; and 
 issue a CT decision to the ingress tile by the egress buffer component, the CT decision indicating whether to transition the output port to the CT state, 
 wherein a packet arrived at the ingress tile is held from processing until the CT decision is returned. 
 
     
     
       3. The network switch of  claim 1 , comprising:
 at least one ingress controller configured to:
 when the output port is in the CT state, forward one or more packets to a CT path within the network switch to send the one or more packets directly to a read launcher of the network switch; and 
 when the output port is in the SAF state, forward the one or more packets to an SAF path within the network switch to pass the one or more packets through one or more processes and to the read launcher. 
 
 
     
     
       4. The network switch of  claim 3 , wherein a CT queue is maintained for a packet through the CT path and a SAF queue is maintained for a packet through the SAF path. 
     
     
       5. The network switch of  claim 3 , wherein the one or more processes include processes by a source context block, an OQS block, and a ToQ block. 
     
     
       6. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 determine that a new packet is not granted CT access, the new packet having newly arrived during the CT state of the output port; 
 transition the output port from the CT state to a CT reject state during which one or more CT packets remaining in an egress buffer are drained, the CT packets having been received at the egress buffer via a CT path within the network switch during the CT state of the output port; and 
 transition the output port from the CT reject state to the SAF state when the one or more remaining CT packets in the egress buffer are drained. 
 
     
     
       7. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 determine that the output port is empty during the SAF state; and 
 transition the output port directly from the SAF state to the CT state when the output port is empty. 
 
     
     
       8. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 determine that a fill level of the output port is below a threshold during the SAF state; and 
 transition the output port from the SAF state to the TCT state in response to determining that the fill level is below the threshold. 
 
     
     
       9. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 determine whether one or more SAF packets remaining in an egress buffer are drained from the egress buffer, the SAF packets having been received the egress buffer via an SAF path within the network switch during the SAF state of the output port; and 
 transition the output port from the TCT state to the CT state when the one or more remaining SAF packets are drained from the egress buffer. 
 
     
     
       10. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 determine to transition the output port back to the SAF state when one or more packets to be sent to an SAF path within the network switch have been received during the TCT state; 
 transition the output port from the TCT state to a TCT fail state to drain packets received during the TCT state upon determining to transition the output port back to the SAF state; and 
 transition the output port from the TCT fail state to the SAF state when remaining packets that have remained in the egress buffer since before the transition to the TCT fail state have been drained from the egress buffer. 
 
     
     
       11. The network switch of  claim 1 , wherein the at least one egress controller is configured to:
 grant a higher priority to CT packets on a CT path within the network switch than to SAF packets on a SAF path within the network switch; and 
 output the CT packets and the SAF packets based on the priority. 
 
     
     
       12. The network switch of  claim 1 , wherein the at least one egress controller is further configured to:
 determine a burst of cells to an egress buffer block while the output port is in the CT state; and 
 absorb the burst in the egress buffer block without transitioning the output port out of the CT state. 
 
     
     
       13. The network switch of  claim 1 , wherein the at least one egress controller is further configured to:
 determine an order of arrival of packets at the network switch; and 
 transmit the packets out of the network switch in the order of arrival. 
 
     
     
       14. A method comprising:
 determining to transition an output port of a network switch between a store-and-forward (SAF) state and a cut-through (CT) state based on at least one factor; 
 transitioning, based on a condition of the output port, the output port to a transition-cut-through (TCT) state or directly to a CT state when transitioning the output port to the CT state; and 
 when the output port is transitioned to the TCT state, determining, based on the condition of the output port, whether to transition the output port to the CT state or to revert back to the SAF based on a condition of the output port. 
 
     
     
       15. The method of  claim 14 , further comprising:
 determining that a new packet is not granted CT access, the new packet having newly arrived during the CT state of the output port; 
 transitioning the output port from the CT state to a CT reject state during which one or more CT packets remaining in an egress buffer are drained, the CT packets having been received at the egress buffer via a CT path within the network switch during the CT state of the output port; and 
 transitioning the output port from the CT reject state to the SAF state when the one or more remaining CT packets in the egress buffer are drained. 
 
     
     
       16. The method of  claim 14 , further comprising:
 determining that the output port is empty during the SAF state; and 
 transitioning the output port directly from the SAF state to the CT state when the output port is empty. 
 
     
     
       17. The method of  claim 14 , further comprising:
 determining that a fill level of the output port is below a threshold during the SAF state; and 
 transitioning the output port from the SAF state to the TCT state in response to determining that the fill level is below the threshold. 
 
     
     
       18. The method of  claim 14 , further comprising:
 determining whether one or more SAF packets remaining in an egress buffer are drained from the egress buffer, the SAF packets having been received the egress buffer via an SAF path within the network switch during the SAF state of the output port; and 
 transitioning the output port from the TCT state to the CT state when the one or more remaining SAF packets are drained from the egress buffer. 
 
     
     
       19. The method of  claim 14 , further comprising:
 determining to transition the output port back to the SAF state when one or more packets to be sent to an SAF path within the network switch have been received during the TCT state; 
 transitioning the output port from the TCT state to a TCT fail state to drain packets received during the TCT state upon determining to transition the output port back to the SAF state; and 
 transitioning the output port from the TCT fail state to the SAF state when remaining packets that have remained in an egress buffer since before the transition to the TCT fail state have been drained from the egress buffer. 
 
     
     
       20. A system comprising:
 a plurality of input ports configured to receive one or more packets; 
 an ingress tile connected to the plurality of input ports to receive the one or more packets via the plurality of input ports; and 
 one or more egress buffer components connected to one or more output ports to transmit the one or more packets received from the ingress tile, wherein each of the one or more egress buffer components is configured to:
 determine to transition a respective output port between a store-and-forward (SAF) state and a cut-through (CT) state based on at least one factor, 
 transition the respective output port to a transition-cut-through (TCT) state or directly to a CT state when transitioning to the CT state, and 
 when the respective output port is transitioned to the TCT state, transition, based on a condition of the output port, the respective output port to the CT state or to revert back to the SAF.